Carbon-Hydrogen Activation of Ketones by 2-Phenylazophenylgold(III) Complexes to give Ketonylgold(III) Complexes

Abstract

Complexes [AuR(acac-C)CI] {R = pap (C,H,N=NPh-2) la or mpap [C,H,(N=NC,H4Me-4)-2-Me-5] 1 b; Hacac = acetylacetone} or 'AuR(CI)(OCIO,)' (R = pap 2a or mpap 2b) react with various ketones MeC(0)R' to give [AuR{CH,C(O)R'}CI] [R = pap, R' = Et 3, Pr" 4, Pr' 5, Bui 6 or C,H,(OMe),-3,4,5 7; R = mpap, R' = Me 81. Whereas la does not react with MeC(O)CH,CI, 2a gives a mixture of the expected [Au(pap){CH,C(O)CH,CI}CI] and [Au(pap)Cl,J. However, other ketones [R'C(O)R''] (R' = Me; R" = Ph, CH,=CH, trans-PhCH=CH or MeCO; R' = R" = CH,CI or Et) or 2-methylcyclohexanone do not react at room temperature with 2a. The reactions of 2a with other species containing activated methyl groups [MeCO,Et, MeC(O)NH, or MeCN] either do not occur or give products in which there is no carbonhydrogen activation. Thus, 2a reacts with dimethyl sulfoxide (dmso) to give the first organogold(iii) complex with this ligand, [Au(pap)(dmso),J [CIO,], 9. It reacts with Nal to give [Au(pap)CI(I)] 10. Complex 8 reacts with NaCI0,-H,O and pyridine (py) or 2,2'-bipyridine (bipy) to give [Au(mpap)(CH,C(O)Me>L]ClO, (L = py 11 or bipy 12). The following reactions were also studied: [Au(pap)Cl(acac-C)] + PPh, or AgCIO, to give [Au(pap)Cl(acac-C)(PPh,)] 13 or [Au(pap)(acac- 0,O')l Cli3,14, respectively. Complexes 13 and 14 do not give an acetonyl complex with acetone; 14 is the first cationic acetylacetonatogold( lit) complex. A plausible reaction pathway is proposed for ketone carbon-hydrogen activation starting from complexes 2. Low-temperature crystal structures were determined for [Au(mpap)CI,] [space group PT, a = 7.902(2), b = 9.527(2), c = 10.378(3) A, x = 86.77(2), p = 77.32(2), y = 67.42(2)", R = 0.0241 and 11 [space group P2,/n, a = 8.693(5), b = 15.800(8), c = 16.489(8) A, j3 = 94.51 (4)", R = 0.0271. The latter is the first crystal structure of an acetonylgold(iii) complex, and it could be shown conclusively that the CH,C(O)Me group is bonded through the carbon atom. Both structures show the expected square-planar co-ordination around the gold atom, with some distortion from the narrow chelate rings. In the first complex the higher trans influence of the aryl group leads to a lengthening of the trans Au-CI bond (2.347 A) with respect to the cis bond (2.274 A).